[Expansional limitation of facial nerve: an experimental study on rabbits].
OBJECTIVE: To investigate expansional limitation of facial nerve. METHODS: Buccal branches of rabbit facial nerves were transected middly and the proximal and distal nerve stumps were lengthened separately by the expander which was designed by the authors. According to the principle of orthogonal design, 25 proximal and 25 distal stumps were lengthened up to 0%, 10%, 20%, 30%, 40% respectively. The average speed of the elongation was 10 mm per 10 minutes. After the elongation were finished, end to end neurorrhaphy were performed except the 0% group in which 10 mm of the nerve wascut off and then retransplanted. Fifteen weeks later, electromyogram(EMG) of buccal muscle and nerve conductive velocity(NCV) were measured to evaluate the function of repaired nerves. While, the number and diameter of regenerating fibers were counted. RESULTS: Compair Compare to the transplantation group, when the proximal segments were lengthened up over 30%, the result of the repairment would be effected considerably despite the elongation of the distal segments, and when the proximal segments were elongation within 30%, the distal segments could be lengthened up to 40% without significant decrease in the functional index (EMG, NCV). CONCLUSIONS: Deducting the postexpansional retraction, the elongation limit of the proximal segments is 18.7% +/- 2.4%, while the distal segments is 24.9% +/- 2.5%. These should be a referable indications for peripheral nerve especially for facial nerve defect reconstruction.